Mucopolysaccharidoses (MPS) refer to a group of inherited lysosomal storage diseases, each of which is caused by the deficiency of a lysosomal enzyme that degrades glycosaminoglycans (GAGs). MPS patients exhibit undegraded GAGs in lysosomes, leading to lysosomal distention and progressive cellular and organ dysfunction, caused by accumulation of chondroitin, dermatan and heparan sulphate. Patients afflicted with MPS can have a variety of clinical features including short stature, progressive bone and joint abnormalities termed dysostosis multiplex, course facial features, deafness, corneal clouding, hepatosplenomegaly, mental retardation and premature death. The lysosomal storage defect can occur in the viscera, brain and skeleton, and the accumulated GAGs have a fibrillogranular appearance ultrastructurally (Vogler et al., J. Inher. Metab. Dis. 21:575–586, 1998).
One member of this disease group is a hereditary retinal disease caused by β-glucuronidase deficiency. Also known as MPS VII, it is a progressive condition, with most tissues affected including the CNS.
Canine and murine models of MPS VII have been described (Haskins et al., Pediatr Res 18:980–984, 1984, Birkenmeier et al., J Clin Invest 83:1258–1256, 1989). The MPS mouse shares many common features with human patients, including the ocular pathology (Li and Davidson, PNAS 92:7700–7704, 1995; Volger et al., Am J Pathol 136:207–217, 1990). These shared features make the MPS mouse an attractive model for studying experimental treatment of a lysosomal disease. For example, cells in diseased tissues contain numerous distended lysosomes. In the brain, both neurons and cells of glial lineage are affected. In the eye, the retinal pigment epithelium (RPE) is affected.
Gene therapy has been used to treat a variety of disorders and gene transfer to the eye has been attempted using recombinant vectors such as adenovirus (Li et al., Invest Opthalmol Vis Sci 35:2543–2549, 1994; Borras et al., Gene Ther 6:515–524, 1999; Li and Davidson, PNAS 92:7700–7704, 1995; Sakamoto et al., H Gene Ther 5:1088–1097, 1999) adeno-associated virus (Ali et al., Hum Gene Ther 9:81–86, 1998, Flannery et al., PNAS 94:6916–6921, 1997; Bennett et al., Invest Opthalmol Vis Sci 38:2857–2863, 1997; Jomary et al., Gene Ther 4:683–690, 1997, Rolling et al., Hum Gene Ther 10:641–648, 1999; Ali et al., Hum Mol Genet 5:591–594, 1996) and human immunodeficiency virus (Miyoshi et al., PNAS 94:10319–23, 1997; Takahashi et al., J Virol 73:7812–7816, 1999). Each of these viruses infect slightly different populations of cells. For example, an intravitreal injection of adenovirus infects cells only in the anterior segment of the eye, mainly the corneal endothelium and iris pigmented epithelium, while a subretinal injection results mainly in positive RPE and muller cells (Li et al., Invest Opthalmol Vis Sci 35:2543–2549, 1994; Li and Davidson, PNAS 92:7700–7704, 1995; Sakamoto et al., H Gene Ther 5:1088–1097, 1999. AAV injected intravitreally results in transduction of the ganglion-cell layer and the RPE. A subretinal injection produces positive photoreceptors, in addition to the RPE and ganglion cells (Ali et al., Hum Mol Genet 5:591–594, 1996). Studies with HIV injected subretinally have shown efficient transduction of the RPE and photoreceptors (Miyoshi et al., PNAS 94:10319–23, 1997; Takahashi et al., J Virol 73:7812–7816, 1999).
Recombinant retroviral gene delivery methods have been extensively utilized in other gene therapy approaches, in part due to: (1) the efficient entry of genetic material (the vector genome) into cells; (2) an active, efficient process of entry into the target cell nucleus; (3) relatively high levels of gene expression; (4) the potential to target particular cellular subtypes through control of the vector-target cell binding and the tissue-specific control of gene expression; (5) a general lack of pre-existing host immunity; (6) substantial knowledge and clinical experience which has been gained with such vectors; and (7) the capacity for stable and long-term expression.
Briefly, retroviruses are diploid positive-strand RNA viruses that replicate through an integrated DNA intermediate. Upon infection by the RNA virus, the retroviral genome is reverse-transcribed into DNA by a virally encoded reverse transcriptase that is carried as a protein in each retrovirus. The viral DNA is then integrated pseudo-randomly into the host cell genome of the infected cell, forming a “provirus” which is inherited by daughter cells.
One type of retrovirus, the murine leukemia virus, or “MLV”, has been widely utilized for gene therapy applications (see generally Mann et al. Cell 33:153, 1983; Cane and Mulligan, PNAS 81:6349, 1984; and Miller et al., Human Gene Therapy 1 :5–14, 1990). One major disadvantage of MLV-based vectors, however, is that the host range (i.e., cells infected with the vector) is limited, and the frequency of transduction of non-replicating cells is generally low.
Feline immunodeficiency virus (“FIV”)-mediated gene therapy vector systems have also been described (see, International Publication Nos. WO 99/15641 and WO 99/36511).
The present invention provides compositions and methods for treating and preventing a number of retinal and brain diseases and degenerations such as RP and AMD, using retrovirus-mediated gene transfer and, further, provides other related advantages.